/**
 * Unit-API - Units of Measurement API for Java (http://unitsofmeasurement.org)
 * Copyright (c) 2005-2011, Unit-API contributors, JScience and others
 * All rights reserved.
 *
 * See LICENSE.txt for details.
 */
package org.unitsofmeasurement.test.unit;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.HashMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.logging.Level;
import java.util.logging.Logger;

import org.unitsofmeasurement.quantity.Area;
import org.unitsofmeasurement.quantity.Dimensionless;
import org.unitsofmeasurement.quantity.Information;
import org.unitsofmeasurement.quantity.Length;
import org.unitsofmeasurement.quantity.Quantity;
import org.unitsofmeasurement.quantity.Volume;
import org.unitsofmeasurement.unit.Unit;

/**
 * A factory producing simple quantities instances (tuples {@link Number}/
 * {@link TestUnit}).
 *
 * For example:
 *
 * [code]
 *   Mass m = QuantityFactory.getInstance(Mass.class).create(23.0, KILOGRAM); // 23.0 kg
 *   Time m = QuantityFactory.getInstance(Time.class).create(124, MILLI(SECOND)); // 124 ms
 * [/code]
 *
 * @param <Q>
 *            The type of the quantity.
 *
 * @author <a href="mailto:desruisseaux@users.sourceforge.net">Martin Desruisseaux</a>
 * @author <a href="mailto:units@catmedia.us">Werner Keil</a>
 * @author <a href="mailto:jean-marie@dautelle.com">Jean-Marie Dautelle</a>
 * @version 1.1
 */
abstract class QuantityFactory<Q extends Quantity<Q>> {
    /**
     * Holds the current instances.
     */
    @SuppressWarnings("rawtypes")
    private static final ConcurrentHashMap<Class, QuantityFactory> INSTANCES =
            new ConcurrentHashMap<Class, QuantityFactory>();

    private static final Logger logger = Logger.getLogger(QuantityFactory.class.getName());

    private static final Level LOG_LEVEL = Level.FINE;

    /**
     * Returns the default instance for the specified quantity type.
     *
     * @param <Q>
     *            The type of the quantity
     * @param type
     *            the quantity type
     * @return the quantity factory for the specified type
     */
    @SuppressWarnings("unchecked")
    public static <Q extends Quantity<Q>> QuantityFactory<Q> getInstance(final Class<Q> type) {
        logger.log(LOG_LEVEL, "Type: " + type + ": " + type.isInterface());
        QuantityFactory<Q> factory;
        if (!type.isInterface()) {
            if (type != null && type.getInterfaces() != null & type.getInterfaces().length > 0) {
                logger.log(LOG_LEVEL, "Type0: " + type.getInterfaces()[0]);
                Class<?> type2 = type.getInterfaces()[0];
                factory = INSTANCES.get(type2);
                if (factory != null) {
                        return factory;
                }
                if (!Quantity.class.isAssignableFrom(type2)) {
                    // This exception is not documented because it should never happen if the
                    // user don't try to trick the Java generic types system with unsafe cast.
                    throw new ClassCastException();
                }
                factory = new Default<Q>((Class<Q>) type2);
                INSTANCES.put(type2, factory);
            } else {
                factory = INSTANCES.get(type);
                if (factory != null) {
                    return factory;
                }
                if (!Quantity.class.isAssignableFrom(type)) {
                    // This exception is not documented because it should never happen if the
                    // user don't try to trick the Java generic types system with unsafe cast.
                    throw new ClassCastException();
                }
                factory = new Default<Q>(type);
                INSTANCES.put(type, factory);
            }
        } else {
            factory = INSTANCES.get(type);
            if (factory != null) {
                return factory;
            }
            if (!Quantity.class.isAssignableFrom(type)) {
                // This exception is not documented because it should never happen if the
                // user don't try to trick the Java generic types system with unsafe cast.
                throw new ClassCastException();
            }
            factory = new Default<Q>(type);
            INSTANCES.put(type, factory);
        }
        return factory;
    }

    /**
     * Overrides the default implementation of the factory for the specified
     * quantity type.
     *
     * @param <Q>
     *            The type of the quantity
     * @param type
     *            the quantity type
     * @param factory
     *            the quantity factory
     */
    @SuppressWarnings("rawtypes")
    protected static <Q extends Quantity> void setInstance(final Class<Q> type, QuantityFactory factory)
    {
        if (!Quantity.class.isAssignableFrom(type)) {
            // This exception is not documented because it should never happen if the
            // user don't try to trick the Java generic types system with unsafe cast.
            throw new ClassCastException();
        }
        INSTANCES.put(type, factory);
    }

    /**
     * Returns the quantity for the specified number stated in the specified
     * unit.
     *
     * @param value
     *            the value stated in the specified unit
     * @param unit
     *            the unit
     * @return the corresponding quantity
     */
    public abstract Q create(Number value, Unit<Q> unit);

    /**
     * Returns the metric unit for quantities produced by this factory or
     * <code>null</code> if unknown.
     *
     * @return the metric units for this factory quantities.
     */
    public abstract Unit<Q> getMetricUnit();

    /**
     * The default factory implementation. This factory uses reflection for
     * providing a default implementation for every {@link QuantityAmount}
     * sub-types.
     *
     * @param <Q>
     *            The type of the quantity
     */
    private static final class Default<Q extends Quantity<Q>> extends QuantityFactory<Q> {
        /**
         * The type of the quantities created by this factory.
         */
        private final Class<Q> type;

        /**
         * The metric unit for quantities created by this factory.
         */
        private final Unit<Q> metricUnit;

        /**
         * Creates a new factory for quantities of the given type.
         *
         * @param type
         *            The type of the quantities created by this factory.
         */
        @SuppressWarnings("unchecked")
        Default(final Class<Q> type) {
            this.type = type;
            metricUnit = CLASS_TO_METRIC_UNIT.get(type);
        }

        @SuppressWarnings("rawtypes")
        static final HashMap<Class, Unit> CLASS_TO_METRIC_UNIT = new HashMap<Class, Unit>();
        static {
            CLASS_TO_METRIC_UNIT.put(Dimensionless.class, TestUnit.ONE);
            // CLASS_TO_METRIC_UNIT.put(Mass.class, KILOGRAM);
            CLASS_TO_METRIC_UNIT.put(Length.class, DistanceUnit.REF_UNIT);
            // CLASS_TO_METRIC_UNIT.put(AmountOfSubstance.class, MOLE);
            // CLASS_TO_METRIC_UNIT.put(Time.class, SECOND);
            // CLASS_TO_METRIC_UNIT.put(MagnetomotiveForce.class, AMPERE_TURN);
            // CLASS_TO_METRIC_UNIT.put(Angle.class, RADIAN);
            // CLASS_TO_METRIC_UNIT.put(SolidAngle.class, STERADIAN);
            CLASS_TO_METRIC_UNIT.put(Information.class, BitUnit.REF_UNIT);
            // CLASS_TO_METRIC_UNIT.put(Frequency.class, HERTZ);
            // CLASS_TO_METRIC_UNIT.put(Force.class, NEWTON);
            // CLASS_TO_METRIC_UNIT.put(Pressure.class, PASCAL);
            // CLASS_TO_METRIC_UNIT.put(Energy.class, JOULE);
            // CLASS_TO_METRIC_UNIT.put(Power.class, WATT);
            // CLASS_TO_METRIC_UNIT.put(ElectricCharge.class, COULOMB);
            // CLASS_TO_METRIC_UNIT.put(ElectricPotential.class, VOLT);
            // CLASS_TO_METRIC_UNIT.put(ElectricCapacitance.class, FARAD);
            // CLASS_TO_METRIC_UNIT.put(ElectricResistance.class, OHM);
            // CLASS_TO_METRIC_UNIT.put(ElectricConductance.class, SIEMENS);
            // CLASS_TO_METRIC_UNIT.put(MagneticFlux.class, WEBER);
            // CLASS_TO_METRIC_UNIT.put(MagneticFluxDensity.class, TESLA);
            // CLASS_TO_METRIC_UNIT.put(ElectricInductance.class, HENRY);
            // CLASS_TO_METRIC_UNIT.put(LuminousFlux.class, LUMEN);
            // CLASS_TO_METRIC_UNIT.put(Illuminance.class, LUX);
            // CLASS_TO_METRIC_UNIT.put(Radioactivity.class, BECQUEREL);
            // CLASS_TO_METRIC_UNIT.put(RadiationDoseAbsorbed.class, GRAY);
            // CLASS_TO_METRIC_UNIT.put(RadiationDoseEffective.class, SIEVERT);
            // CLASS_TO_METRIC_UNIT.put(CatalyticActivity.class, KATAL);
            // CLASS_TO_METRIC_UNIT.put(Velocity.class, METRES_PER_SECOND);
            // CLASS_TO_METRIC_UNIT.put(Acceleration.class,
            // METRES_PER_SQUARE_SECOND);
            CLASS_TO_METRIC_UNIT.put(Area.class, AreaUnit.REF_UNIT);
            CLASS_TO_METRIC_UNIT.put(Volume.class, VolumeUnit.REF_UNIT);
        }

        @Override
        @SuppressWarnings("unchecked")
        public Q create(final Number value, final Unit<Q> unit) {
            // System.out.println("Type: " + type);
            return (Q) Proxy.newProxyInstance(type.getClassLoader(),
                    new Class<?>[] { type }, new GenericHandler<Q>(value, unit));
        }

        @Override
        public Unit<Q> getMetricUnit() {
            return metricUnit;
        }
    }

    /**
     * The method invocation handler for implementation backed by any kind of
     * {@link Number}. This is a fall back used when no specialized handler is
     * available for the number type.
     */
    private static final class GenericHandler<Q extends Quantity<Q>>
            implements InvocationHandler
    {
        final Unit<Q> unit;
        final Number value;

        GenericHandler(final Number value, final Unit<Q> unit) {
                this.unit = unit;
                this.value = value;
        }

        @SuppressWarnings({ "unchecked", "rawtypes" })
        public Object invoke(final Object proxy, final Method method, final Object[] args) {
            final String name = method.getName();
            if (name.equals("doubleValue")) { // Most frequent.
                final Unit<Q> toUnit = (Unit<Q>) args[0];
                if ((toUnit == unit) || (toUnit.equals(unit))) {
                    return value.doubleValue(); // Returns value directly.
                }
                return unit.getConverterTo(toUnit).convert(value.doubleValue());
            } else if (name.equals("longValue")) {
                final Unit<Q> toUnit = (Unit<Q>) args[0];
                if ((toUnit == unit) || (toUnit.equals(unit))) {
                    return value.longValue(); // Returns value directly.
                }
                double doubleValue = unit.getConverterTo(toUnit).convert(value.doubleValue());
                if ((doubleValue < Long.MIN_VALUE) || (doubleValue > Long.MAX_VALUE)) {
                    throw new ArithmeticException("Overflow: " + doubleValue
                                    + " cannot be represented as a long");
                }
                return (long) doubleValue;
            } else if (name.equals("getValue")) {
                return value;
            } else if (name.equals("getUnit")) {
                return unit;
            } else if (name.equals("toString")) {
                final StringBuilder buffer = new StringBuilder();
                return buffer.append(value).append(' ').append(unit).toString();
            } else if (name.equals("hashCode")) {
                return value.hashCode() * 31 + unit.hashCode();
            } else if (name.equals("equals")) {
                final Object obj = args[0];
                if (!(obj instanceof Quantity)) {
                    return false;
                }
                final Quantity that = (Quantity) obj;
//              if (!unit.isCompatible((AbstractUnit<?>) that.getUnit())) {
//                  return false;
//              }
//              return value.doubleValue() == (that).doubleValue(unit);
                return equals(that);
            } else if (name.equals("compareTo")) {
                final Quantity that = (Quantity) args[0];
//              return Double.compare(value.doubleValue(), that.doubleValue(unit));
                return equals(that);
            } else {
                throw new UnsupportedOperationException(name);
            }
        }
    }
}
